Part 2: Do you have IBS?

Maybe you think you’ve got IBS, but you’re not sure; maybe you’re not actually sure what it means to have IBS. This short article explains how we as doctors diagnose IBS. With around 10% of the population estimated to have IBS, not all will have been diagnosed.

It’s a diagnosis of exclusion

This means that we only diagnose people with irritable bowel syndrome (IBS) once we’ve ruled out every other cause for their symptoms. Things we commonly rule out include: coeliac disease, inflammatory bowel disease (IBD) and cancers (in the older population). We can normally do this with some simple questions, a blood test and maybe a stool sample. Once we’re sure it’s not something else, we can start to think about diagnosing IBS. This doesn’t mean we’ve given up, it simply reflects that 1) IBS is still poorly understood and that 2) it’s more difficult to diagnose than other health conditions.

The Rome III Criteria

Criteria are often used to make diagnoses in the NHS. They are based on evidence from scientific research. For IBS, we can use something called the Rome III criteria (III because it’s been refined over time and Rome because…? Presumably, an acronym for the research it’s based on!):

Recurrent abdominal pain or discomfort for 3 days per month in the last 3 months (12 weeks), associated with ≥2 of the criteria below, for at least six months:

You feel much better once you’ve gone for a poo

Your bowel habit has changed so you’re going more frequently or less frequently than usual

Your poo looks different than normal – sometimes people are given a diagnosis of C-IBS or D-IBS which stands for constipation- and diarrhoea-predominant IBS respectively, or, you might have more of a mixed picture

If you are experiencing two or more of these symptoms, you may have IBS. It’s important to rule out the other diseases mentioned above because they are treated differently. For example, coeliac requires a small bowel biopsy to be diagnosed and IBD is treated with set medications which are not used for IBS. Bowel cancer is also associated with having a change in bowel habit and is clearly a serious illness that needs to be excluded. Contact your GP if your bowels are playing up, especially if you have worrying symptoms like blood in your poo, persistent diarrhoea (because you are at risk of becoming dehydrated) and weight loss and vomiting.

If you’ve got a diagnosis already, watch this space for current recommended treatments for IBS!